The following discussion is intended to facilitate the understanding of the invention, but is not intended nor admitted to be prior art to the invention.
Obesity is a public health problem that is serious, widespread, and increasing. In the United States, 20 percent of the population is obese; in Europe, a slightly lower percentage is obese [Friedman (2000) Nature 404:632-634]. Obesity is associated with increased risk of hypertension, cardiovascular disease, diabetes, and cancer as well as respiratory complications and osteoarthritis [Kopelman (2000) Nature 404:635-643]. Even modest weight loss ameliorates these associated conditions.
Maintenance of weight gain or loss is associated with compensatory changes in energy expenditure that oppose the maintenance of a body weight that is different from the usual weight [Leibel et al. (1995) N Engl J Med 332:621-8]. These changes may account, in part, for the poor long-term efficacy of obesity treatments [Wadden (1993) Ann Intern Med 229:688-93]. Further, the decreased insulin sensitivity after weight gain and the beneficial effects of even modest amounts of weight reduction on carbohydrate metabolism and insulin sensitivity in some patients are well documented [Olefsky et al. (1974) J Clin Invest 53:64-76].
While still acknowledging that lifestyle factors including environment diet, age and exercise play a role in obesity, twin studies, analyses of familial aggregation, and adoption studies all indicate that obesity is largely the result of genetic factors [Barsh et al. (2000) Nature 404:644-651]. In agreement with these studies, is the fact that an increasing number of obesity-related genes are being identified. Some of the more extensively studied genes include those encoding leptin (ob) and its receptor (db), pro-opiomelanocortin (Pomc), melanocortin-4-receptor (Mc4r), agouti protein (Ay), carboxypeptidase E (fat), 5-hydroxytryptamine receptor 2C (Htr-2c), nescient basic helix-loop-helix 2 (Nhlh2), prohormone convertase 1 (PCSK1), and tubby protein (tubby) [rev'd in Barsh et al. (2000) Nature 404:644-651].